1. Field of the Invention
The present invention relates to a high-density plasma processing apparatus. More particularly, the present invention relates to a high-density plasma processing apparatus that is designed to improve uniformity of a distribution of plasma near a surface of a substrate.
2. Description of the Related Art
Plasma application techniques are widely used in a process of microfabricating a substrate used to manufacture a semiconductor device or a flat display panel. In particular, plasma is widely used to etch the surface of a wafer used to manufacture a semiconductor device or the surface of a substrate used to manufacture a liquid crystal display (LCD). In addition, plasma is widely used to deposit a predetermined material layer on the surface of the substrate or wafer. Accordingly, development of a plasma processing apparatus suitable for a wafer etching process or a process of depositing a layer on a wafer is critical to the development of methods and apparatuses for manufacturing a semiconductor device or a flat display panel.
There are a variety of types of conventional plasma processing apparatuses that are presently in widespread use, including an inductively coupled plasma (ICP) processing apparatus and a plasma processing apparatus using microwaves.
FIG. 1 illustrates a schematic structure of a conventional ICP processing apparatus. Referring to FIG. 1, the conventional ICP processing apparatus includes a processing chamber 10 defining a plasma forming space. A susceptor 12 is installed at an inner bottom surface of the processing chamber 10 to support an object to be processed, e.g., a wafer (W). A dielectric window 16 is installed on top of the processing chamber 10 to form a top surface of the processing chamber 10. A gas inlet 14 for introducing a reaction gas into the processing chamber 10 is formed through one sidewall of the processing chamber 10. A plurality of gas distribution ports 15, which is connected to the gas inlet 14, is formed within the processing chamber 10. A vacuum suction port 18, which is connected to a vacuum pump 19, is formed through a bottom wall of the processing chamber 10. The vacuum pump 19 evacuates air from the processing chamber 10 through the vacuum suction port 18 to create vacuum conditions within the processing chamber 10, thereby sealing the processing chamber 10. An ICP antenna 20 for generating plasma within the processing chamber 10 is installed over the dielectric window 16.
An RF power supply (not shown) is connected to the ICP antenna 20. Accordingly, an RF current flows through the ICP antenna 20 and generates a magnetic field. Due to a change in the magnetic field with time, an electric field is induced within the processing chamber 10. At this time in an operation of the apparatus, the reaction gas is introduced into the processing chamber 10 via the gas distribution ports 15. Electrons accelerated by the induced electric field then ionize the reaction gas by colliding with the reaction gas, thereby generating a plasma within the processing chamber 10. The generated plasma is used to etch a surface of the wafer W while chemically reacting with the surface of the wafer W or to deposit a predetermined material layer on the surface of the wafer W.
FIG. 2 illustrates a conventional plasma processing apparatus using microwaves. The plasma processing apparatus of FIG. 2 includes a plasma source 40 and a processing chamber 30. The plasma source 40 includes a microwave generator (not shown), a waveguide 41, and a radiative tube 42. The waveguide 41 transfers a microwave oscillated by the microwave generator and has a rectangular cross-section. The radiative tube 42 has a plurality of slots 43 for radiating the microwave into the processing chamber 30. The slots 43 may be formed in various shapes.
The processing chamber 30 includes a dielectric window 31, a support 32, and gas inlets 33. The dielectric window 31 is installed on top of the processing chamber 30, and the radiative tube 42 is installed on the dielectric window 31. The support 32 for supporting an object to be processed, e.g., a wafer, is installed within the processing chamber 30 opposite to the dielectric window 31. The support 32 is connected to a power supply 35. An exhaust port 34 is formed through a bottom wall of the processing chamber 30 and used to create vacuum conditions within the processing chamber 30.
In conventional plasma processing apparatuses having structures such as those described above, the distribution of plasma near a wafer is not uniform.
FIGS. 3A and 3B are graphs showing a relationship between a distribution of plasma through a plasma generating area within a processing chamber and a distribution of plasma near a wafer. As shown in FIG. 3A, even when plasma is uniformly distributed through the plasma generating area, a distribution of plasma near the wafer is non-uniform due to diffusion. Hence, to obtain uniform distribution of plasma near the wafer, it is desirable to form a plasma distribution having a plasma density greater near a peripheral area of an interior of the processing chamber than near a central area, i.e., an “M-shaped” plasma distribution, through the plasma generating area, as shown in FIG. 3B.
When the distribution of plasma is non-uniform as described above, an etching depth of the wafer W or a thickness and property of a material layer deposited on the surface of the wafer W varies over the surface of the wafer W.
In particular, this variation becomes severe as a size of a substrate increases. In the case of ICP processing apparatuses, as the substrate becomes larger, a size of an ICP antenna used must be larger in order to maintain a high plasma density within a processing chamber. However, since a voltage applied to the ICP antenna necessarily increases with the enlargement of the ICP antenna, there is a limit in enlarging the ICP antenna. In addition, in the case of plasma processing apparatuses using microwaves, transmitting the high power of the microwave to the interior of a processing chamber without a substantial increase in the size of a microwave source is difficult, and uniformly distributing the power of a microwave into the processing chamber is also difficult.
As described above, the conventional plasma processing apparatuses are not able to satisfactorily cope with a change in process conditions because of the aforementioned problems and accordingly can provide neither a high plasma density nor a uniform distribution of plasma. In particular, with a recent trend toward the enlargement of a wafer, it becomes more difficult for the conventional plasma processing apparatuses to maintain the uniformity of the distribution of plasma near a wafer. This non-uniformity significantly degrades the quality or yield of semiconductor devices. Therefore, both an improvement in the uniformity of a wafer processing process with an enlarged wafer and maintenance of a high plasma density are primary considerations in the development of a plasma processing apparatus.